[Bug translator/12740] New: excessive memory use for pouchless @entry constructs

["fche at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=12740

           Summary: excessive memory use for pouchless @entry constructs
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap@sourceware.org
        ReportedBy: fche@redhat.com


The auxiliary arrays used for saved context variables / @entry expressions
from return probes are too big & numerous.  We need either uretprobe data
pouches, or an optimized representation of @entry.


% stap -v -e 'probe process("stap").function("*").return { v = now() -
@entry(now()); println(v) } function now() { return gettimeofday_us() }' -c
'stap -h'

Pass 1: parsed user script and 79 library script(s) using
99264virt/25924res/2684shr kb, in 260usr/30sys/289real ms.
Pass 2: analyzed script: 3926 probe(s), 4 function(s), 4 embed(s), 3926
global(s) using 268464virt/58368res/11444shr kb, in 14640usr/230sys/15014real
ms.

>>>> 15 seconds elapsed

Pass 3: translated to C into
"/tmp/stapMeJZN3/stap_ef8438e9fd2f330188d9cba770d94d23_2125712.c" using
269384virt/61608res/11468shr kb, in 1820usr/440sys/2253real ms.
In file included from /usr/share/systemtap/runtime/transport/transport.c:61,
                 from /usr/share/systemtap/runtime/print.c:18,
                 from /usr/share/systemtap/runtime/runtime.h:128,
                 from
/tmp/stapMeJZN3/stap_ef8438e9fd2f330188d9cba770d94d23_2125712.c:55:
/usr/share/systemtap/runtime/transport/control.c: In function
â_stp_ctl_write_cmdâ:
/usr/share/systemtap/runtime/transport/control.c:28: note: variable tracking
size limit exceeded with -fvar-tracking-assignments, retrying without
Pass 4: compiled C into "stap_ef8438e9fd2f330188d9cba770d94d23_2125712.ko" in
247980usr/6720sys/259102real ms.

>>>> lots of seconds elapsed; results in 20MB source, 17MB .ko

[4869689.454921] stap_b8c8890dfa144b224309c3548d29adbe_2159197: systemtap:
1.4/0.152, base: ffffffffa09d5000, memory:
2899data/2326text/7ctx/13net/479488alloc kb, probes: 3926

>>>> and an awesome quantity of runtime memory consumption

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